Multiple Choice
Which of the following statements correctly describes the pH scale?
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17. Acid and Base Equilibrium
The pH Scale
Multiple Choice
On the pH scale at , the pH of a basic (alkaline) aqueous solution is typically:
A
Equal to
B
Greater than
C
Less than
D
Always equal to
Verified step by step guidance1
Recall that the pH scale measures the acidity or basicity of an aqueous solution, where pH is defined as \(\mathrm{pH} = -\log[\mathrm{H}^+]\).
Understand that at 25°C, pure water is neutral with a pH of 7, meaning the concentration of hydrogen ions \([\mathrm{H}^+]\) equals the concentration of hydroxide ions \([\mathrm{OH}^-]\).
Recognize that a basic (alkaline) solution has a lower concentration of hydrogen ions than pure water, so \([\mathrm{H}^+] < 10^{-7}\) M.
Since pH is the negative logarithm of the hydrogen ion concentration, a lower \([\mathrm{H}^+]\) means a higher pH value, so the pH of a basic solution is greater than 7.
Note that the pH scale typically ranges from 0 to 14 at 25°C, where pH 7 is neutral, values less than 7 are acidic, and values greater than 7 are basic.
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